The standard deviation of the starter salary for economics students graduation is 4200. Calculate the probability that sample mean of 40 student(x.bar) will be bigger than mean of the total population (mu)
In general I need to calculate what is P(x.bar>mu)
Aside of calculating the SED I don't know how to continue.
It is just as likely the mean of $40$ students is above the population mean as below the population mean, and hence the probability is $50\%$.
(By the way, the title is extremely misleading, given you never have to "find sample mean.")